What is ladder logic?
Ladder Logic is a programming language that creates and displays a program using ladder diagrams based on circuit diagrams. It is mainly used in developing programs or software for programmable logic controllers (PLC) used in industrial applications.
The language originally evolved from a method of documenting the design and construction of relay racks used in manufacturing and process control, with each relay rack represented by an icon on the ladder diagram with connections to devices below that look like vertical rails. The relay symbols themselves look like rungs in a ladder.
Ladder logic is described as a rule-based language rather than procedural or imperative language. Each 'sprog' in the ladder represents a rule, so when these rules are implemented for relays and various electromechanical devices, they will be executed simultaneously and instantaneously. However, when the program is applied to PLCs, the rules are executed sequentially through software and in a continuous loop. If the loop is executed fast enough, the effect will still act like simultaneous and immediate execution within the required time tolerance. The capabilities of the PLC used must be taken into account during programming as the electromechanical properties of the devices connected to it may not be able to keep up with the instructions and it seems that some rules are being skipped if the devices really cannot continue.
Ladder logic is widely used in industrial environments to program PLCs that require sequential control of manufacturing processes and operations. The programming language is very useful for programming simple but critical systems or for reworking old hard-wired systems into newer programmable ones. This programming language is also used in sophisticated automation systems such as electronics and car factories.
The idea behind the ladder logic is that even people without a programming background can program quickly because they use conventional and familiar construction symbols for programming. This advantage is quickly lost, however, as PLC manufacturers often also provide ladder logic programming systems with their products that sometimes do not use the same symbols and conventions as those used for other models of third-party PLCs; In fact, the programming system is usually only intended for certain models, so the programs cannot easily be ported to other PLC models or have to be completely rewritten.